you could but the problem here is how long is the aftermarket cat? the older rangers used a precat/cat setup and that was about 30 inches long, an aftermarket cat is only about 1 foot long. so youll need couplers and a piece of pipe not to mention 6 clamps, 2 for the front of the cat at the coupler/original pipe, 2 for after the cat to a piece of pipe, 2 more for the preexisting pipe to the new pipe. another thing to consider is what shape is the outlet from the y pipe, if im not mistake the pipe is ovular to the cat, not round so youd have to fabricate that mount as well if the cat is coming directly from the y pipe. whats wrong w/ your cat?